Chem Basics

Chem Basics:

atoms:basic unit of matter

• the subatomic particles that make up atoms are protons, neutrons, and electrons
• atos are extremely small
• protons and neutrons have the same mass
• protons are positively charged, neutrons have no charge, and electrons are negatively charged
• protons and neutrons are bond together to form the nucleus
• electrons are in constant motion in the space surrounding the nucleus

elements and isotopes:

• an element is a pure substance that consists entirely of one type of element
• an isotope is an atom of an element that has anumber of neutrons different from that of other atoms of the same element
• all isotopes have the same chemical properties, beacause they have the same number of electrons

chemical bonds: the main types of chemical bonds are ionic and covalent bonds

• ionic bond is formed when one or more electrons are transferred from one atom to another
• covalent bond forms when electrons are shared between atoms
• the electrons available to form bonds are called valence electrons
• atoms that lose electrons have a positive charge
• atoms that gain electrons have a negative charge
• when the atoms share two electrons, the bond is called a single covalent bond

van der Waals forces: a slight attraction that develops between the oppositely charged regions of nearby molecules

• are not as strong as covalent and ionic bonds
• can hold molecules together
• ex) van der Waals forces help geckos grip smooth, vertical surfaces

water molecule:

• a water molecule is neutral
• polar molecule: molecule in which the charges are unevenly distributed
• a water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms

hydrogen bonds:

• not as strong as covalent or ionic bonds
• ex) the attraction between the hydrogen atom on one water molecule and the oxygen atom on another water molecule
• water is etremely cohesive, due to hydrogen bonding

acids, Bases, and pH:

• ph scale:
  • scale ranges from 0 to 14
  • solutions with a pH below 7 are acidic, solutions with a ph above 7 are basic, and solutions with the pH of seven are neutral( pure water has a pH of seven)
• acidic solutions contain higher concentrations of H+ ions than pure water and have pH values lower than 7
  • ex) stomach acid, lemon juice, tomato juice, acid rain, and normal rainfall
• basic, or alkaline, solutions contain lower concentrations of H+ ions than pure water and have a pH above 7
  • ex) oven cleaner, bleach, ammonia solution. soap, sea water, and human blood

videos:

• Making Molecules with Atoms
• Ionic and covalent bonding animation
• Bill Nye the science guy: Atoms and Molecules